Milo g



(No Model.)

M. G. KELLOGG. MULTIPLE SWITGHBOARD.

@Hozmmda Nrrnn STATES PA'f'rEN'r rFIcE.

MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGG SWITCI-IBOARD AND SUPPLY COMPANY, OF SAME PLACE.

MULTIPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent No. 592,409, dated October 26, 1897. Application filed August 31, 1891. Renewed December 30,1893. Serial No. 495,261. (No model.)

To all whom t may concern:

Be it known that I, MILO G. KELLOGG, of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Multiple Switchboards for Telephone-Exchan ges, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

.My invention relates especially to a telephone-exchange system in which inductioncoil translators or converters, one for each line at the central oflice, are employed to translate the telephone-currents from one circuit or line to another circuit or line.

It consists in a system of answering-calls, clearin g-out signals, and calling from the central office which I shall describe and claim in detail.

In the drawings and in the description of the system I indicate the lines as metalliccircuit lines. The invention is, however, applicable to other kinds of lines, as groundcircuit lines.

In the accompanying drawings, illustrating my invention, Figure l represents sectional `views of two switchboards with the centralofiice switches and apparatus for two lines of the exchange and the connecting and answering apparatus at each board for answering calls, connecting the translators of the two lines, testing to see whether the lines are in use, and receiving clearing-out signals for a connection which may be made. Fig. 2 shows in diagram a subscribers-station apparatus to be used in the exchange system.

In Fig. l, A A' are two switchboards. Other boards may be added and used as required for the size of the exchange. Each board has a metal socket or switch contactpiece for each line. These sockets or contact-pieces are marked jj and are each adapted to receive the switch-plugs at the boards and thereby form contact with the contact-piece of the plug and also to have the test-plug contact-pieces applied to them for testing, as will hereinafter be described. I I are two inw 'w are two annunciators, one for (marked D D,) a test-battery for the pair of plugs, (marked B,) a clearing-out annunciator for the pair of plugs, (marked 11,) an operators telephone, (marked t,) a switch for the pair of plugs, (marked Y,) and a callinggenerator, (marked B.) The switch Y has a lever and three contact-bolts on which the lever may alternately be placed. The plugs of a pairarc connected together by iiexible conductors, and in the circuit between them is their test-battery B'. Each plug is adapted to be placed in connection with each metal socket j at its board.

The lever of lthe switch is connected to the circuit which connects the two plugs preferably so that the battery B is in circuit between the lever and the plug D. One side of the telephone, one side of the calling-generator, and one side of the clearing-out annunciator are connected with the three contact-bolts, respectively,of the switch Y. The other sides of the telephone, calling-generator, and clearing-out annunciator are connected together by metal conductors, and are connected by metal conduct-ors with the same side of the various other instruments of the same kind in the exchange. One side of one of the coils of each translator is connected by a metal conductor with the same sides of these instruments.

i c' are induction-coils, and T T are testplugs, one of each for each operator. One coil of each of these induction-coils is in circuit with the telephone of the opera-tor. The test-plug 'Il is connected to a iieXible conductor adapted to be brought for testing into connection with` each .contact-piece j at its board and is connected through the other coil of the induction-coil with the metal conductor mentioned above.

Only one pair of plugs with their special IOO lzo

vss-

vin Fig. 2, l is the telephone-switch; 2, the

signal-receiving bell;l 3,. the calling-generator; 4, vthe subscribers telephone, ,andl 5 a calling-key. The circuits and contacts are substantially as shown and may be in other wayswhich will carry out. substantially the operations whichA will hereinafter'be described; When; the key. 5.\ i's. pressed., the line-circuit is-grounded, at the centralofice. @therwise theline-circuit is:notgroundedthere When thegenerator is operated, it. isin the-metallic circuit off the, line. When the telephone is on theswtch, the signal-bellzis in the-direct circuit. ot the line,` and. when. the telephone. is off the switchit is itselfy in the direct: circuit oi the, line..

The operation ofthe system isasfollows: When a subscriber wishestomal'lea call`,.he he presses on his key 5 andwhi'le doing so operatesnhis callingj-generator.l Acalling-currentv then; passesQi'n; a, circuit fromthe grou-nd at. his stationth-rough that side or. branch: of theline.l im which. the generator is tio-ground at thccentra'loftice throughiheline-annunciator andoperatesthea-nnunciator.V Part offthecursrent generatedwillipass throughlthe-complete metallic circuit on the line, but enough. will pass through lche gro und-circuit: traced; above tdcpera-tethe.-annunciator. When-the opera'- tor to-Who'm the-annunciator. is assigned; ob.-

. serves the call,` she. placesI oneof' her. switch.-

plugs: Dtinftothe metal soeketof. the line-at her board-1 and. moves-the lever ot thesWitch-.Y belonginggtothe plug so that hertelephonie is in connection with it. A completemetallic'circuit-is thus establishedin which. is included theoperators. telephone and. one coil of. thel tra-nslatoroftheline; The subscriber having taken: his telephone from-.its switch, `the telephone.T is included in a: direct metallic circuit with the, lineand the other coil of the transv lator.. The. subscriber and-operator may then converse. 'andi the subscriber gi-ve hise call. 'Ilheoperator then tests-the line-Wan ted, as will bedescribed, 'and if it isnot in use. places the Y mate-tothe plug (marked D!) into` the metal Y rllheA locall socket of the other line-Wanted.. coil of. .the translatorv of the line Wanted is thereby connectedi-n a metallic circuit with the: local-1 coilf of the calling-line,.and this circuit has the'test-battery B' of the pair-offp'lugs in'M it. andis-bridged or cross-connectediby the operators; telephone: The operatorn then movestheleverof the-switch Y so that it is in connection. with thecalling-generator and the generator isin a bridge-circuitk of the me*- v tallic circuit containing the two coils, and the generator being operated f a current goes through both coils and an induced current isl ,3 bridge or cross connection of the metallic cir- 4 "cuit which contains the two translator-coils. The subscribers can then converse, the telei phone-currents being translated from one metallic-circuit line to the metallic circuit which "contains the two-local coils and from said circuit to the other metallic-circuit lincs. l

When a subscriber Wishes to senda clearing-outA signal, he operates his calling-generator/wiithout4 pressing. on. his key 5. A current is thereby generated in his metallic-circuit. linel and an induced current is generated `in:y the local coil of the line, which Will: operate the-clearing-out annunciator. which is in fcircu'iti with. such. coil, (being in a cross-connecting circuit to the circuit of the two local coils of thelines.) The operation of the test system is as follows: When theoperator wishes-to test a line Wanted to determine whether it is inuse, she placesher test-plug T on. the contact-piece j at her boardof the line to be tested. If, then, the'line has-a switch-'plug in one of its cong tact-piccesj at another board, az complete j' circuit. is established. Whichrcontains one coil of her induction-coil il and the battery B', which is in circuit with the switch-plugwhich iis in, saidi contact-piece j. A current will therefore pass through. the coil` which will cause an. induced current in the othercoil and occasion a click in the operators telephone.. y It there isl no plug in any contactlpie'cej-of theline,no suchcomplete circuit is established. whichy contains the coil ot her induction-coilv and a1 battery, and the click will not be'maidein her telephone. She can therefore determine on testing Whether or not. the r`line is-inzuse.

The closed circuit of the telephone and secondaryof the induction-coil. when. a. test is made is, sayfro1n plug D in the contactpiecey off thefcallingf-line, thence through the I translator-coil of the line-to the common wire which unites-` the translatorcoils thence through the telephone and` secondaryof the induction-coil t' to the lever of the switch Y, and thence through the flexible cord to D..

The `complete circuit mentioned above as established when a4 plugisin acontact-piecej `of the line; is, say, from the metal conductor x heretofore mentionedthrough the coil of the Ainduction-coil tothe test-plug T, thence to the contact-piecej, where the test is made, 'thence to the contact-piece j inv which'is the *twitch-plug, and thence throughk the battery in circuit with the plug and alocal coil convnectedv with it to said metal conductor..

The connections-.of the local coils of the IOO translator' and of the operators apparatus to the same are all metallic and without ground connection or circuit, and therefore when two coils are connected together for purposes of conversation the circuit is not subject to interference from earth currents or connections. These advantages would to a certain extent be obtained should the metallic-circuit connection I have described be purposely7 or accidentally connected with the ground at a certain point.

The invention is applicable to other ar rangements of circuits and apparatus than that described-as, for instance, a single testbattery may be used for the exchange connected into the metal conductor, so that the test-plugs T T are connected on one side of the battery and the switches Y Y are connected on the other side of the battery.

rIhe induction-coils it' with their telephones t t may be considered as test :receiving instruments, Other forms of test receiving instruments may be used.

It will be observed that when the two local coils of two line-translators are connected together into a complete metallic circuit and are left for conversation between the two subscribers the circuit is bridged or cross-cen neeted between the two coils by the clearingout annunciator. It is preferable that the annunciator be of such a construction as to offer considerable retardation to the passage of telephone-currents, and such cross connection will not greatly affect the amount of telephone-current which would otherwise pass through the complete circuit.

I claim as my inventionl. In atelephone-exchange system, two metallic-circuit lines and translators at the central oiiice for said lines, one coil of each of which is in the circuit of its line, the two other coils of the translators being temporarily connected for conversation in a complete metallic circuit, in combination with a clean ing-out annunciator in a bridge connection across said metallic circuit between said coils.

2. In a telephone-exchange system, two metallic-circuit lines and translators at the cerr tral oftice for said lines, one translator for each line, one coil of which is in the circuit of the line, the two other coils of the translators being temporarily connected in metal lic circuit for conversation, in combination with a bridge connection across said metallic circuit, an operators calling-generator and a switch to at will include said generator in said bridge connection.

3. In a telephoneexchange system, two telephone-lines and translators at the central ofiice for said lines, one translator for each line, one coil of which is in the circuit of the line, the other two coils of the translators being temporarily connected together for conversation in a complete metallic circuit, in combination with a clearing-out annunciator in a bridge or cross connection to said metallic circuit between the two coils.

4. In a telephone-exchange system, two metallic-circuit lines and translators at the central office for said lines, one coil of each of which is in the circuit of its line, the two other coils of the translators being temporarily connected for conversation in a complete metallic circuit, in combination with a retardation apparatus in a bridge connection across said metallic circuit between said coils.

5. In a telephone-exchange system, two telephone-lines and translators at the central office for said lines, one translator for each line, one coil of which is in the circuit of the line, the other two coils of the translators being temporarily connected together for conversation in a complete metallic circuit, in combination with a retardation apparatus in a bridge or cross connection to said metallic circuit between the two coils.

In testimony whereof I have hereunto subscribed my name.

MILO G. KELLOGG. Vitnesses FRANCES D. KELLoGG, ANNA I. KnLLoc'G. 

